"I don't know if someone is acting in our name, but what I'm sure about is that JEM would not do such a thing," he said.

The employees were taken hostage on October 18 in Korodofan outside Darfur, a region of western Sudan that has been the scene of a nearly six-year war.

Two escaped with injuries and two other workers remained in captivity, according to the Sudanese government.

China's ambassador to Khartoum and senior Chinese officials flew to Kordofan to recover the bodies of the five oil workers.

Oil ally

China is the main buyer of Sudan's oil, a key economic investor and perhaps Khartoum's most powerful foreign ally.

This has drawn criticism in the West that China has not done enough to help bring an end to the conflict in Darfur and on occasions shielded the Khartoum government from international pressure.

Jiang said China would maintain strong ties with Sudan's government, despite the killings.

"In the future we will continue to value and implement a friendly policy towards Sudan," she said.

"[But] meanwhile we hope that Sudan will provide good conditions for the people to people relations between the two countries."

Kidnappings

The government in Khartoum has labelled JEM a "terrorist" organisation and the group attacked the Sudanese capital last May.

In the past, Darfur fighters have kidnapped foreign oil workers from Sudanese oilfields, often targeting Chinese companies because of their strong ties with Khartoum, although all of those abducted eventually emerged unscathed.

In October 2007, JEM attacked an oilfield run by the Greater Nile Petroleum Operating Company, a consortium involving China's CNPC. JEM said the oilfield was a legitimate military target.

The Saudi-owned Asharq Al-Awsat newspaper last week identified the alleged leader of the kidnappers as Abu Humaid Ahmad Dannay, who reportedly said he commands JEM in Kordofan and belongs to the Arab Messeria tribe.

The Messeria were blamed for kidnapping four Indian oil workers and their Sudanese driver in the same area in May. All five escaped or were released.